Electrode catheters have been in common use in medical practice for many years. They are used to stimulate and map electrical activity in the heart and to ablate sites of aberrant electrical activity.
In use, an electrode catheter is inserted into a major vein or artery, e.g., femoral artery, and then guided into the chamber of the heart which is of concern. Within the heart, the ability to control the exact position and orientation of the catheter tip is critical and largely determines how useful the catheter tip is.
Steerable tip electrode catheters are well known. Such a catheter generally has a control handle at its proximal end for controlling deflection of the tip in one or more directions. For example, a particularly useful steerable tip catheter is disclosed in U.S. Pat. Nos. 4,960,134 and Re. 34,502 to Webster, the disclosures of which are hereby incorporated by reference. This catheter comprises a puller wire which extends on-axis through an elongated reinforced catheter body and then off-axis in a deflectable tip portion. In this arrangement, longitudinal movement of the puller wire relative to the catheter body results in deflection of the catheter tip portion. Other examples of steerable catheters can be found in U.S. Pat. No. 5,431,168 to Webster and U.S. patent application Ser. No. 08/924,611 to Webster entitled "Omni-Directional Steerable Catheter," the disclosures of which are hereby incorporated by reference.
U.S. Pat. No. 5,391,199 to Ben-Haim, discloses a non-deflectable electrode catheter with an imaging system for the treatment of cardiac arrhythmias, the disclosure of which is hereby incorporated by reference. The electrode catheter comprises an electromagnetic sensor adjacent the tip electrode at the distal tip of the catheter. The system allows an operator to create a three dimensional image of the heart chamber and to monitor the position of the sensor, and hence the tip electrode within that three dimensional image of the heart chamber. The electromagnetic sensor disclosed is generally cylindrical and has a relatively large outside diameter of about 6 to 7 French (1 French=approximately 0.013 inch). This large diameter creates numerous difficulties in designing a small diameter, e.g., 8 French, steerable catheter incorporating an electromagnetic sensor. Further, the sensor must be completely insulated from the electrodes and electrode lead wires to perform properly.
In addition, the presence of the electromagnetic sensor along with the tip electrode imparts rigidity to the distal end of the catheter tip section. These characteristics create further difficulties in designing a small diameter, steerable catheter comprising an electromagnetic sensor.